1. Field of the Invention
The present invention relates to a method of processing mixtures of organic substances, including high boiling point constituents and/or constituents which do not boil but which melt, by extraction with supercritical solvents.
2. Description of the Related Art
German Auslegeschrift No. 1,493,190, which corresponds to U.S. Pat. No. 3,969,196, discloses a separation process employing supercritical gases for the separation of mixtures of substances which are liquid and/or solid under the process conditions and contain organic compounds and/or compounds including organic groups. According to this process, solids, such as naphthalene, phenanthrene or anthracene, and also natural substances, such as camphor or chlorophyll, can be taken into the supercritical phase like components or mixtures of substances which are liquid under process conditions.
German Patentschrift No. 3,114,593, which corresponds to U.S. Pat. No. 4,400,398, discloses a process for the recovery of aromatics and coloring matter from red peppers by means of a supercritical solvent. Useful solvents described therein include carbon dioxide, ethane, ethene and a mixture of ethane and ethene.
German Auslegeschrift No. 2,127,618, which corresponds to U.S. Pat. No. 4,104,409, discloses a method of producing hop extracts by the extraction of air-dried hops with a supercritical solvent.
European Patent Application No. 232,481 discloses a process for the production of hard coal tar pitch raw materials which are obtained from a supercritical solution by extraction with a supercritical gas and an entraining agent, and fractions are separated by stepwise changes in pressure and temperature. Aliphatic hydrocarbons having two to five carbon atoms and olefinic carbons having two to five carbon atoms, as well as halogen-containing hydrocarbons having one to four carbon atoms, are mentioned as specific solvents.
The production of montan wax from peat moss or soft coal by extraction with a supercritical solvent is disclosed in German Patent Application P 3,714,452. This application discloses CO.sub.2, aliphatic hydrocarbons having two to five carbon atoms, petroleum ether, and water as useful solvents.
Because of poor yields, however, the prior art methods are generally unsatisfactory from an economic point of view and do not sufficiently exploit the raw materials.